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Written by David R. Hassall, WA5DJJ
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Saturday, 18 June 2005 |
My PIXIE interest started about two years ago when I was looking
for a simple transceiver to be built by my builders group that would
give a successful contact among the members and provide an effective
tool for exploring the art of building a working radio. Here I'll
outline what I've done with the PIXIE and where you can find out more
if you want to build a PIXIE.
| My
first PIXIE was built for show and tell to the group. I built it
"Manhattan Style" using parts scrounged from old VCR's , Telephones,
Computer modems, etc. From that time on I was hooked on the little
radio. My 1st is pictured at the right. It used a switch to offset the
frequency between transmitt and receive. |
|  | After
operating it for a short while, I noticed the little things that escape
you when your first doing a project like this. My CW skills are not the
best and the radio didn't have a sidetone Oscillator so I could hear
what I was sending. After looking at a number of designs I settled on
the one in W1FB's book using two NPN transistors. I changed another
resistor in the PIXIE so that the audio amp didn't mute completely and
I was in business. I made some local contacts with my builders group
members but any DX seemed to elude me. My side tone was built on a
separate piece of PC board and wrapped in Black tape to keep it from
shorting out the other stuff and "stuffed" into the Altoids can. It is
pictured at left. | | After some
more study and revising my layout to accomidate changes and having much
difficulty modifying my first PIXIE. I decided to build unit #2. It has
the side tone oscillator laid out on the main board and another
automatic switching circuit to provide the frequency offset for the
transmitter every time the key was depressed. It really worked better
and I tried numerous times to work some DX and was finally successful
working a station 875 miles away. But the QRM was terrible. But even
with that, the little radio performed well with only 440 Milliwatts of
RF output on 40 meters to a simple Dipole antenna. |  |
| Still
thinking I could improve the number of contacts per CQ, I surmised that
the little radio wasn't putting out enough power to be heard. So I set
about to build myself a QRP Gallon Linear. I settled on the design from
NORCAL that was used to boost the output of the SMT transciever. It was
a simple linear using a Radio Shack Fet transistor. I added a switching
circuit from W1FB's Design Notebook to switch the linear inline for
transmit and out of line for receive. Now my little radio had a 3.5
watt voice and I was heard more often. The linear is pictured left. | | Since
my CW skills are slow (15 wpm Max) and pushing down a hand key for a
long period of time makes my arm ache. I built myself a computer
interface that would key the PIXIE and my ROCKMITE by just typing on
the keyboard using the HAMCOM program. That really eased the stress on
my old bones and made operating much easier. The PIXIE receiver does
not have enough signal strength to lock up the CW decoder in the HAMCOM
program but it does sometimes lock up with the ROCKMITE receiver and is
great for reading the mail. From the success of the decoder I don't
think I am the only one using this method. |  |
| So
what is next? Well, The QRM problem is the next big hurtle to solve.
There are a couple of interesting filter circuits that I am trying to
get to work that should fit between the detector and the LM386 audio
amplifier. To ease the strain of development of modifications for the
PIXIE, I have devised a LARGE SIZE PIXIE that I built on a piece of
particle board that I use for building my modifications on. It is
pictured at left and has one of the audio filter circuits already built
on it ready for some serious testing. Another modification I would like
to make on Linear is to switch in a receiver RF amplifier/preselector
when the linear is in the receive position. I think that would help the
PIXIE's receiver sensitivity. | | | | | | |
I
will keep working on this little wonder as a matter of choice. It is
the ultimate in "bare bones" radios. By all accounts, it is about as
minimal as you can go and still have something that works. It is a
great Club builders project. Most of the parts can be scrounged from
defunct consumer electronics such as VCR's, Telephones, Computer
Modems, Boom Boxes, and the like. It is simple to build Manhattan Style
which eliminates the need for a Printed Circuit board. About the only
parts that you really have to buy are the crystal, the LM386 Audio
Amplifier and the core to wind the output filter inductor on. It is
about as close to a "FREE" radio as you can get. Here is a picture of
my complete PIXIE station that I take with me when I travel. The power
supply in the black block is 8 AA penlite batteries in two 4 battery
holders hooked in series to give me 12 volts. The headphnes are a pair
of Walkman type made by Koss that I got at Walmart for $5.99 and has a
small volume control mounted in the cord. The Key is an old Radio Shack
Hand Key that I have had for years. If you don't have a hand key there
is a number of ways to make one. (one design uses a large paper clip
and works great). The PIXIE is set to operate at 7040Khz and my normal
antenna is the simple dipole strung up as best I can where ever I am
visiting. A modified PAC-12 antenna for 40 meters has also been tried
but the dipole just seemed to work better, even at low altitudes.
Here are the links to the information that I studied on the PIXIE Transceiver concepts that I used to make my PIXIE's.
http://www.al7fs.us/AL7FS2.html this link to Jim's site explains how his adaptation of the PIXIE works and pictures and information on how his was built.
http://www.qrpp-i.com/ This site is the mother load of articles on the PIXIE transceiver. It contains many links to sites with building tips, available kits, and operating hints in building and using the PIXIE.
If
you need additional information on My PIXIE Experiments, feel free to
email me, I would be glad to hear from you. You can email me at:
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